I'm up, I'm up.
For me, the Hitchcock films were pure entertainments, and I didn't realize until much later how influential they were. So, whilst I enjoyed them and loved them and revered them, they did not make me see movies differently. Here are some that I saw as a youngster that did (all on their first release):
Psycho (yes, a Hitchcock film, but one that had sport with all the rules - after Psycho, I trusted no film to play by the rules. In terms of structure and style, one of the most imitated films ever made).
Sundays and Cybele - I'd never seen a film quite like it - weird, poetic, with images so beautiful and stark and with a plot so peculiar that it introduced me to a whole new style of cinema.
The Umbrellas Of Cherbourg - really a one-off film that created its own unique world in a way that hadn't been done before - and succeed in doing so by not only being a marvelous film, but by being a huge hit.
A Hard Day's Night - again, so influential, style-wise, that it's been copied by so many people for so many years that it's hard to watch it and understand just how radical it was.
Bonnie and Clyde - again, its style and way of presenting its "heroes" was completely unique for the time, and its ending influenced many filmmakers.